Why does my neutral wire at the fuse box glow red when nothing is switched on?

Finding a glowing red neutral wire in your fuse box is genuinely alarming, and your concern is completely justified. That red glow is heat, and heat in electrical wiring is one of the leading causes of house fires in the UK. Here is what is most likely happening and what you should do. What the neutral wire normally does In a standard UK single-phase supply, the neutral wire completes the circuit back to the transformer on the street. Under normal conditions it should carry roughly the same current as the live wire, and it should stay cool. If it is glowing red, it is getting far too hot. The most common reasons this happens 1. Loose or corroded connection at the neutral bar inside the consumer unit. A poor connection creates resistance, and resistance turns electrical energy into heat. Even small amounts of current can cause serious overheating at a bad joint. 2. Overloaded neutral conductor. If multiple circuits share a neutral, an imbalance can cause the neutral to carry more current than it was designed for. 3. Lost or broken neutral on the incoming supply. If the neutral from the street is faulty, strange voltages can appear across your wiring and some conductors can overheat unexpectedly. 4. Damaged or undersized cable. If a previous repair used the wrong cable size, the conductor may not be rated for the current it is carrying. What you should do right now Switch off the main switch on your consumer unit. This is the large switch usually at the top left or top right of the board. Do not switch individual breakers back on to investigate. Do not assume the problem has gone away once the wire cools down. Call a registered electrician straight away. Look for someone on the NICEIC, NAPIT, or Electrical Competent Person register. This is a Category 1 level danger and in EICR terms would be coded as a C1, meaning danger present and immediate action required. Do not attempt to open the consumer unit yourself, re-tighten terminals yourself, or use the circuits until a professional has inspected and repaired the fault. The glowing wire you can see may be the symptom of a deeper problem that is not visible without proper testing.